1. Field of the Invention
The present invention relates to an image forming apparatus in which a finisher such as a sorter for after-treating a sheet of recording paper is additionally disposed in an image forming body section. More particularly, the present invention relates to a paper conveying mechanism for conveying the sheet of recording paper supplied to the image forming apparatus.
2. Description of the Related Art
As is well known, a finisher is additionally disposed in various kinds of image forming apparatuses such as a copying machine, a printer, a facsimile, etc. in a certain case. The finisher is composed of a sorter, etc. for sorting sheets of recording paper in an image forming body section.
In a general image forming body section, the sheets of recording paper are discharged and sorted in a side region of this body section. The general image forming apparatus is of such a side operating type in many cases.
Accordingly, the image forming body section has a conveying path for conveying the sheets of recording paper from one side portion to the other side portion so as to form an image. The above finisher is connected in parallel to an outlet portion of the above conveying path in the image forming body section, i.e., a side portion of the image forming body section.
However, in such an image forming apparatus, the image forming body section is of the side operating type as mentioned above so that a horizontal size of the entire apparatus is increased. Further, recorded sheets of recording paper having an image thereon are taken out of a tray and a paper supplying cassette having unrecorded sheets of recording paper therein is attached to the image forming body section on both sides of the image forming apparatus. Accordingly, it is necessary to dispose a space for performing the above-mentioned operations on both sides of the image forming apparatus.
It is further necessary to afford a margin of this space such that no pedestrian hits against the tray, etc. Accordingly, when the image forming apparatus is arranged, it is necessary to dispose a space having a size larger than that of a space required to perform the actual operation of the apparatus in consideration of the above-mentioned situations. Therefore, there is a case in which the various kinds of operations mentioned above cannot be sufficiently performed when such an image forming apparatus is arranged within a relatively small space.
To solve such problems, it is considered to arrange the above conveying path for the sheets of recording paper on front and rear sides of the image forming body section in a direction perpendicular to this conveying path. Such a structure is shown in e.g., Japanese Patent Application No. 1-150842 having the same applicant as this application.
However, in the image forming apparatus having the conveying path as mentioned above, for example, when the sheets of paper are continuously supplied, it is necessary that a subsequent sheet of recording paper does not interfere with a preceding sheet of recording paper when the conveying directions of the sheets of recording paper are switched. Therefore, the reduction of a moving speed of the continuously supplied sheets of paper is restrained by increasing a conveying distance between the sheets of recording paper or increasing the moving speed of the sheets when the sheets are conveyed in a perpendicular direction. However, in such a method, conveying distances are changed in accordance with kinds of the conveyed sheets of paper. Therefore, a control operation for switching the conveying speeds in accordance with the kinds of the conveyed sheets of paper is considerably complicated.
Further, the general image forming apparatus is set such that a sheet of recording paper having a maximal length can be conveyed, thereby causing the following problems.
Namely, copy modes are composed of modes of a single-sided copy, a two-sided (double-sided) copy and a synthetic copy on a single side in the above-mentioned image forming apparatus. The size of a member for conveying the sheets of recording paper is set in the image forming apparatus such that the sheets of recording paper corresponding to the respective copy modes can be sufficiently conveyed. Paper sizes generally used are composed of B4, A4 and B5 in many cases. A4 and B5 are often used for the two-sided copy.
The conveying path is set to convey the sheets of recording paper having a size larger than sizes having a high copy frequency. Accordingly, when such a conveying path is used to convey the sheets of recording paper of the sizes having a high copy frequency, a time from an image forming operation to the next image forming operation in the case of the two-sided copy is especially increased. Therefore, it takes much time to perform a copying operation, thereby reducing copying efficiency.
In a structure in which the sheets of recording paper are discharged onto an upper face of the image forming apparatus, there is a possibility that a base for arranging an original thereon overlaps a position for setting the original since this base is located on the upper face of the apparatus. Accordingly, it is difficult to perform the copying operation while the operation of the base and the original setting operation are separately performed.
It is further difficult to connect a sorter for sorting the discharged sheets of paper, a stapler or another peripheral device to a section for discharging the sheets of recording paper in consideration of their mutual arrangement relations.
Further, the sheets of recording paper are discharged in a state in which an image face is located on upper sides of the sheets of recording paper in many cases. The discharged sheets of paper are fed onto a tray in a page order opposite to that of the original. Accordingly, to obtain the copied sheets of paper in the page order, it is necessary to copy the original from the last page so that the copying operation is complicated. Further, in this case, when a two-sided copying operation is performed from a single-sided original composed of an odd number of sheets, a copied sheet of paper on a first page does not constitute a cover, but is a blank sheet of paper. Images of the original on first and subsequent pages are copied on second and subsequent sheets of paper so that the copying operation is performed in a page order opposite to that of the original.